Reference signal design

ABSTRACT

Certain aspects of the present disclosure relate to methods and apparatus for generating and communicating reference signals. Certain aspects provide a method for communicating reference signals. The method includes selecting a demodulation reference sequence (DMRS) of a plurality of DMRSs for transmission in a synchronization signal block (SSB) based on a half-frame in which the SSB is transmitted. The method further includes transmitting the selected DMRS in the SSB.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent No.62/532,851, filed Jul. 14, 2017. The content of the provisionalapplication is hereby incorporated by reference in its entirety.

INTRODUCTION

Aspects of the present disclosure relate to communication systems, andmore particularly, to methods and apparatuses for generating andcommunicating reference signals.

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,broadcasts, etc. These wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power, etc.). Examples of such multiple-access systems include3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE)systems, LTE Advanced (LTE-A) systems, code division multiple access(CDMA) systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, orthogonal frequency divisionmultiple access (OFDMA) systems, single-carrier frequency divisionmultiple access (SC-FDMA) systems, and time division synchronous codedivision multiple access (TD-SCDMA) systems, to name a few.

In some examples, a wireless multiple-access communication system mayinclude a number of base stations (BSs), which are each capable ofsimultaneously supporting communication for multiple communicationdevices, otherwise known as user equipments (UEs). In an LTE or LTE-Anetwork, a set of one or more base stations may define an eNodeB (eNB).In other examples (e.g., in a next generation, a new radio (NR), or 5Gnetwork), a wireless multiple access communication system may include anumber of distributed units (DUs) (e.g., edge units (EUs), edge nodes(ENs), radio heads (RHs), smart radio heads (SRHs), transmissionreception points (TRPs), etc.) in communication with a number of centralunits (CUs) (e.g., central nodes (CNs), access node controllers (ANCs),etc.), where a set of one or more distributed units, in communicationwith a central unit, may define an access node (e.g., which may bereferred to as a base station, 5G NB, next generation NodeB (gNB orgNodeB), TRP, etc.). A base station or distributed unit may communicatewith a set of UEs on downlink channels (e.g., for transmissions from abase station or to a UE) and uplink channels (e.g., for transmissionsfrom a UE to a base station or distributed unit).

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. New Radio (NR) (e.g., 5G) is an exampleof an emerging telecommunication standard. NR is a set of enhancementsto the LTE mobile standard promulgated by 3GPP. It is designed to bettersupport mobile broadband Internet access by improving spectralefficiency, lowering costs, improving services, making use of newspectrum, and better integrating with other open standards using OFDMAwith a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL).To these ends, NR supports beamforming, multiple-input multiple-output(MIMO) antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues toincrease, there exists a need for further improvements in NR and LTEtechnology. Preferably, these improvements should be applicable to othermulti-access technologies and the telecommunication standards thatemploy these technologies.

BRIEF SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this disclosure provide advantages that include improvedcommunications between access points and stations in a wireless network.

Certain aspects provide a method for communicating reference signals.The method includes selecting a demodulation reference sequence (DMRS)of a plurality of DMRSs for transmission in a synchronization signalblock (SSB) based on a half-frame in which the SSB is transmitted. Themethod further includes transmitting the selected DMRS in the SSB.

Certain aspects provide a wireless device comprising a memory and aprocessor. The processor is configured to select a demodulationreference sequence (DMRS) of a plurality of DMRSs for transmission in asynchronization signal block (SSB) based on a half-frame in which theSSB is transmitted. The processor is further configured to transmit theselected DMRS in the SSB.

Certain aspects provide a wireless device. The wireless device includesmeans for selecting a demodulation reference sequence (DMRS) of aplurality of DMRSs for transmission in a synchronization signal block(SSB) based on a half-frame in which the SSB is transmitted. Thewireless device further includes means for transmitting the selectedDMRS in the SSB.

Certain aspects provide a non-transitory computer readable storagemedium that stores instructions that when executed by a wireless devicecause the wireless device to perform a method for communicatingreference signals. The method includes selecting a demodulationreference sequence (DMRS) of a plurality of DMRSs for transmission in asynchronization signal block (SSB) based on a half-frame in which theSSB is transmitted. The method further includes transmitting theselected DMRS in the SSB.

Aspects generally include methods, apparatus, systems, computer readablemediums, and processing systems, as substantially described herein withreference to and as illustrated by the accompanying drawings.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe appended drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the drawings. It is to be noted, however, thatthe appended drawings illustrate only certain typical aspects of thisdisclosure and are therefore not to be considered limiting of its scope,for the description may admit to other equally effective aspects.

FIG. 1 is a block diagram conceptually illustrating an exampletelecommunications system, in accordance with certain aspects of thepresent disclosure.

FIG. 2 is a block diagram illustrating an example logical architectureof a distributed radio access network (RAN), in accordance with certainaspects of the present disclosure.

FIG. 3 is a diagram illustrating an example physical architecture of adistributed RAN, in accordance with certain aspects of the presentdisclosure.

FIG. 4 is a block diagram conceptually illustrating a design of anexample base station (BS) and user equipment (UE), in accordance withcertain aspects of the present disclosure.

FIG. 5 is a diagram showing examples for implementing a communicationprotocol stack, in accordance with certain aspects of the presentdisclosure.

FIG. 6 illustrates an example of a frame format for a new radio (NR)system, in accordance with certain aspects of the present disclosure.

FIG. 7 illustrates an example of a synchronization signal block (SSB),in accordance with certain aspects.

FIG. 8 illustrates an example of the timing of transmission of SSBs, inaccordance with certain aspects.

FIG. 9 illustrates example operations for wireless communications, forexample, for generating and communicating reference signals, inaccordance with certain aspects.

FIG. 10 illustrates example operations for wireless communications, forexample, for receiving reference signals and determining timinginformation based on the reference signals, in accordance with certainaspects of the present disclosure.

FIG. 11 illustrates a communications device that may include variouscomponents configured to perform operations for the techniques disclosedherein in accordance with aspects of the present disclosure.

FIG. 12 illustrates a communications device that may include variouscomponents configured to perform operations for the techniques disclosedherein in accordance with aspects of the present disclosure.

FIG. 13 illustrates example operations for wireless communications, forexample, for generating and communicating reference signals, inaccordance with certain aspects.

FIG. 14 illustrates a communications device that may include variouscomponents configured to perform operations for the techniques disclosedherein in accordance with aspects of the present disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in one aspectmay be beneficially utilized on other aspects without specificrecitation.

DETAILED DESCRIPTION

Aspects of the present disclosure relate to conveying timing informationregarding a cell to a UE. For example, a base station may generate andtransmit reference signals (e.g., a primary synchronization signal(PSS), a secondary synchronization signal (SSS), and/or a demodulationreference signal (DMRS)) for each cell supported by the base station.The reference signals may be used by UEs for cell detection andacquisition. The base station may also send a Physical Broadcast Channel(PBCH). The PBCH may carry certain system information. The DMRS may beused for channel estimation and demodulation of the PBCH. In certainaspects, the transmission of the reference signals is used to conveytiming information of the cell to the UE. The UE may utilize the timinginformation for synchronization and timing reference for communicatingin the cell. Certain aspects herein relate to communicating information,such as timing information, to the UE based on the design of referencesequences transmitted in the cell.

The following description provides examples, and is not limiting of thescope, applicability, or examples set forth in the claims. Changes maybe made in the function and arrangement of elements discussed withoutdeparting from the scope of the disclosure. Various examples may omit,substitute, or add various procedures or components as appropriate. Forinstance, the methods described may be performed in an order differentfrom that described, and various steps may be added, omitted, orcombined. Also, features described with respect to some examples may becombined in some other examples. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition to,or other than, the various aspects of the disclosure set forth herein.It should be understood that any aspect of the disclosure disclosedherein may be embodied by one or more elements of a claim. The word“exemplary” is used herein to mean “serving as an example, instance, orillustration.” Any aspect described herein as “exemplary” is notnecessarily to be construed as preferred or advantageous over otheraspects.

The techniques described herein may be used for various wirelesscommunication technologies, such as LTE, CDMA, TDMA, FDMA, OFDMA,SC-FDMA and other networks. The terms “network” and “system” are oftenused interchangeably. A CDMA network may implement a radio technologysuch as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRAincludes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implementa radio technology such as Global System for Mobile Communications(GSM). An OFDMA network may implement a radio technology such as NR(e.g. 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRAand E-UTRA are part of Universal Mobile Telecommunication System (UMTS).

New Radio (NR) is an emerging wireless communications technology underdevelopment in conjunction with the 5G Technology Forum (SGTF). 3GPPLong Term Evolution (LTE) and LTE-Advanced (LTE-A) are releases of UMTSthat use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). cdma2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the wireless networks andradio technologies mentioned above as well as other wireless networksand radio technologies. For clarity, while aspects may be describedherein using terminology commonly associated with 3G and/or 4G wirelesstechnologies, aspects of the present disclosure can be applied in othergeneration-based communication systems, such as 5G and later, includingNR technologies.

New radio (NR) access (e.g., 5G technology) may support various wirelesscommunication services, such as enhanced mobile broadband (eMBB)targeting wide bandwidth (e.g., 80 MHz or beyond), millimeter wave (mmW)targeting high carrier frequency (e.g., 25 GHz or beyond), massivemachine type communications MTC (mMTC) targeting non-backward compatibleMTC techniques, and/or mission critical targeting ultra-reliablelow-latency communications (URLLC). These services may include latencyand reliability requirements. These services may also have differenttransmission time intervals (TTI) to meet respective quality of service(QoS) requirements. In addition, these services may co-exist in the samesubframe.

Example Wireless Communications System

FIG. 1 illustrates an example wireless communication network 100 inwhich aspects of the present disclosure may be performed. For example,the wireless communication network 100 may be a New Radio (NR) or 5Gnetwork. For example, BSs of network 100 may transmit reference signalsto UEs of network 100 to communicate information, such as timinginformation, to the UEs based on the design of reference sequencestransmitted in a cell by the BS.

As illustrated in FIG. 1, the wireless network 100 may include a numberof base stations (BSs) 110 and other network entities. A BS may be astation that communicates with user equipments (UEs). Each BS 110 mayprovide communication coverage for a particular geographic area. In3GPP, the term “cell” can refer to a coverage area of a Node B (NB)and/or a Node B subsystem serving this coverage area, depending on thecontext in which the term is used. In NR systems, the term “cell” andnext generation NodeB (gNB), new radio base station (NR BS), 5G NB,access point (AP), or transmission reception point (TRP) may beinterchangeable. In some examples, a cell may not necessarily bestationary, and the geographic area of the cell may move according tothe location of a mobile BS. In some examples, the base stations may beinterconnected to one another and/or to one or more other base stationsor network nodes (not shown) in wireless communication network 100through various types of backhaul interfaces, such as a direct physicalconnection, a wireless connection, a virtual network, or the like usingany suitable transport network.

In general, any number of wireless networks may be deployed in a givengeographic area. Each wireless network may support a particular radioaccess technology (RAT) and may operate on one or more frequencies. ARAT may also be referred to as a radio technology, an air interface,etc. A frequency may also be referred to as a carrier, a subcarrier, afrequency channel, a tone, a subband, etc. Each frequency may support asingle RAT in a given geographic area in order to avoid interferencebetween wireless networks of different RATs. In some cases, NR or 5G RATnetworks may be deployed.

A base station (BS) may provide communication coverage for a macro cell,a pico cell, a femto cell, and/or other types of cells. A macro cell maycover a relatively large geographic area (e.g., several kilometers inradius) and may allow unrestricted access by UEs with servicesubscription. A pico cell may cover a relatively small geographic areaand may allow unrestricted access by UEs with service subscription. Afemto cell may cover a relatively small geographic area (e.g., a home)and may allow restricted access by UEs having an association with thefemto cell (e.g., UEs in a Closed Subscriber Group (CSG), UEs for usersin the home, etc.). A BS for a macro cell may be referred to as a macroBS. A BS for a pico cell may be referred to as a pico BS. A BS for afemto cell may be referred to as a femto BS or a home BS. In the exampleshown in FIG. 1, the BSs 110 a, 110 b and 110 c may be macro BSs for themacro cells 102 a, 102 b and 102 c, respectively. The BS 110 x may be apico BS for a pico cell 102 x. The BSs 110 y and 110 z may be femto BSsfor the femto cells 102 y and 102 z, respectively. A BS may support oneor multiple (e.g., three) cells.

Wireless communication network 100 may also include relay stations. Arelay station is a station that receives a transmission of data and/orother information from an upstream station (e.g., a BS or a UE) andsends a transmission of the data and/or other information to adownstream station (e.g., a UE or a BS). A relay station may also be aUE that relays transmissions for other UEs. In the example shown in FIG.1, a relay station 110 r may communicate with the BS 110 a and a UE 120r in order to facilitate communication between the BS 110 a and the UE120 r. A relay station may also be referred to as a relay BS, a relay,etc.

Wireless network 100 may be a heterogeneous network that includes BSs ofdifferent types, e.g., macro BS, pico BS, femto BS, relays, etc. Thesedifferent types of BSs may have different transmit power levels,different coverage areas, and different impact on interference in thewireless network 100. For example, macro BS may have a high transmitpower level (e.g., 20 Watts) whereas pico BS, femto BS, and relays mayhave a lower transmit power level (e.g., 1 Watt).

Wireless communication network 100 may support synchronous orasynchronous operation. For synchronous operation, the BSs may havesimilar frame timing, and transmissions from different BSs may beapproximately aligned in time. For asynchronous operation, the BSs mayhave different frame timing, and transmissions from different BSs maynot be aligned in time. The techniques described herein may be used forboth synchronous and asynchronous operation.

A network controller 130 may couple to a set of BSs and providecoordination and control for these BSs. The network controller 130 maycommunicate with the BSs 110 via a backhaul. The BSs 110 may alsocommunicate with one another (e.g., directly or indirectly) via wirelessor wireline backhaul.

The UEs 120 (e.g., 120 x, 120 y, etc.) may be dispersed throughout thewireless network 100, and each UE may be stationary or mobile. A UE mayalso be referred to as a mobile station, a terminal, an access terminal,a subscriber unit, a station, a Customer Premises Equipment (CPE), acellular phone, a smart phone, a personal digital assistant (PDA), awireless modem, a wireless communication device, a handheld device, alaptop computer, a cordless phone, a wireless local loop (WLL) station,a tablet computer, a camera, a gaming device, a netbook, a smartbook, anultrabook, an appliance, a medical device or medical equipment, abiometric sensor/device, a wearable device such as a smart watch, smartclothing, smart glasses, a smart wrist band, smart jewelry (e.g., asmart ring, a smart bracelet, etc.), an entertainment device (e.g., amusic device, a video device, a satellite radio, etc.), a vehicularcomponent or sensor, a smart meter/sensor, industrial manufacturingequipment, a global positioning system device, or any other suitabledevice that is configured to communicate via a wireless or wired medium.Some UEs may be considered machine-type communication (MTC) devices orevolved MTC (eMTC) devices. MTC and eMTC UEs include, for example,robots, drones, remote devices, sensors, meters, monitors, locationtags, etc., that may communicate with a BS, another device (e.g., remotedevice), or some other entity. A wireless node may provide, for example,connectivity for or to a network (e.g., a wide area network such asInternet or a cellular network) via a wired or wireless communicationlink. Some UEs may be considered Internet-of-Things (IoT) devices, whichmay be narrowband IoT (NB-IoT) devices.

Certain wireless networks (e.g., LTE) utilize orthogonal frequencydivision multiplexing (OFDM) on the downlink and single-carrierfrequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDMpartition the system bandwidth into multiple (K) orthogonal subcarriers,which are also commonly referred to as tones, bins, etc. Each subcarriermay be modulated with data. In general, modulation symbols are sent inthe frequency domain with OFDM and in the time domain with SC-FDM. Thespacing between adjacent subcarriers may be fixed, and the total numberof subcarriers (K) may be dependent on the system bandwidth. Forexample, the spacing of the subcarriers may be 15 kHz and the minimumresource allocation (called a “resource block” (RB)) may be 12subcarriers (or 180 kHz). Consequently, the nominal Fast FourierTransfer (FFT) size may be equal to 128, 256, 512, 1024 or 2048 forsystem bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz),respectively. The system bandwidth may also be partitioned intosubbands. For example, a subband may cover 1.08 MHz (i.e., 6 resourceblocks), and there may be 1, 2, 4, 8, or 16 subbands for systembandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.

While aspects of the examples described herein may be associated withLTE technologies, aspects of the present disclosure may be applicablewith other wireless communications systems, such as NR. NR may utilizeOFDM with a CP on the uplink and downlink and include support forhalf-duplex operation using TDD. Beamforming may be supported and beamdirection may be dynamically configured. MIMO transmissions withprecoding may also be supported. MIMO configurations in the DL maysupport up to 8 transmit antennas with multi-layer DL transmissions upto 8 streams and up to 2 streams per UE. Multi-layer transmissions withup to 2 streams per UE may be supported. Aggregation of multiple cellsmay be supported with up to 8 serving cells.

In some examples, access to the air interface may be scheduled, whereina. A scheduling entity (e.g., a base station) allocates resources forcommunication among some or all devices and equipment within its servicearea or cell. The scheduling entity may be responsible for scheduling,assigning, reconfiguring, and releasing resources for one or moresubordinate entities. That is, for scheduled communication, subordinateentities utilize resources allocated by the scheduling entity. Basestations are not the only entities that may function as a schedulingentity. In some examples, a UE may function as a scheduling entity andmay schedule resources for one or more subordinate entities (e.g., oneor more other UEs), and the other UEs may utilize the resourcesscheduled by the UE for wireless communication. In some examples, a UEmay function as a scheduling entity in a peer-to-peer (P2P) network,and/or in a mesh network. In a mesh network example, UEs may communicatedirectly with one another in addition to communicating with a schedulingentity.

In FIG. 1, a solid line with double arrows indicates desiredtransmissions between a UE and a serving BS, which is a BS designated toserve the UE on the downlink and/or uplink. A finely dashed line withdouble arrows indicates interfering transmissions between a UE and a BS.

FIG. 2 illustrates an example logical architecture of a distributedRadio Access Network (RAN) 200, which may be implemented in the wirelesscommunication network 100 illustrated in FIG. 1. A 5G access node 206may include an access node controller (ANC) 202. ANC 202 may be acentral unit (CU) of the distributed RAN 200. The backhaul interface tothe Next Generation Core Network (NG-CN) 204 may terminate at ANC 202.The backhaul interface to neighboring next generation access Nodes(NG-ANs) 210 may terminate at ANC 202. ANC 202 may include one or moretransmission reception points (TRPs) 208 (e.g., cells, BSs, gNBs, etc.).

The TRPs 208 may be a distributed unit (DU). TRPs 208 may be connectedto a single ANC (e.g., ANC 202) or more than one ANC (not illustrated).For example, for RAN sharing, radio as a service (RaaS), and servicespecific AND deployments, TRPs 208 may be connected to more than oneANC. TRPs 208 may each include one or more antenna ports. TRPs 208 maybe configured to individually (e.g., dynamic selection) or jointly(e.g., joint transmission) serve traffic to a UE.

The logical architecture of distributed RAN 200 may support fronthaulingsolutions across different deployment types. For example, the logicalarchitecture may be based on transmit network capabilities (e.g.,bandwidth, latency, and/or jitter).

The logical architecture of distributed RAN 200 may share featuresand/or components with LTE. For example, next generation access node(NG-AN) 210 may support dual connectivity with NR and may share a commonfronthaul for LTE and NR.

The logical architecture of distributed RAN 200 may enable cooperationbetween and among TRPs 208, for example, within a TRP and/or across TRPsvia ANC 202. An inter-TRP interface may not be used.

Logical functions may be dynamically distributed in the logicalarchitecture of distributed RAN 200. As will be described in more detailwith reference to FIG. 5, the Radio Resource Control (RRC) layer, PacketData Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer,Medium Access Control (MAC) layer, and a Physical (PHY) layers may beadaptably placed at the DU (e.g., TRP 208) or CU (e.g., ANC 202).

FIG. 3 illustrates an example physical architecture of a distributedRadio Access Network (RAN) 300, according to aspects of the presentdisclosure. A centralized core network unit (C-CU) 302 may host corenetwork functions. C-CU 302 may be centrally deployed. C-CU 302functionality may be offloaded (e.g., to advanced wireless services(AWS)), in an effort to handle peak capacity.

A centralized RAN unit (C-RU) 304 may host one or more ANC functions.Optionally, the C-RU 304 may host core network functions locally. TheC-RU 304 may have distributed deployment. The C-RU 304 may be close tothe network edge.

A DU 306 may host one or more TRPs (Edge Node (EN), an Edge Unit (EU), aRadio Head (RH), a Smart Radio Head (SRH), or the like). The DU may belocated at edges of the network with radio frequency (RF) functionality.

FIG. 4 illustrates example components of BS 110 and UE 120 (as depictedin FIG. 1), which may be used to implement aspects of the presentdisclosure. For example, antennas 452, processors 466, 458, 464, and/orcontroller/processor 480 of the UE 120 and/or antennas 434, processors420, 460, 438, and/or controller/processor 440 of the BS 110 may be usedto perform the various techniques and methods described herein.

At the BS 110, a transmit processor 420 may receive data from a datasource 412 and control information from a controller/processor 440. Thecontrol information may be for the physical broadcast channel (PBCH),physical control format indicator channel (PCFICH), physical hybrid ARQindicator channel (PHICH), physical downlink control channel (PDCCH),group common PDCCH (GC PDCCH), etc. The data may be for the physicaldownlink shared channel (PDSCH), etc. The processor 420 may process(e.g., encode and symbol map) the data and control information to obtaindata symbols and control symbols, respectively. The processor 420 mayalso generate reference symbols, e.g., for the primary synchronizationsignal (PSS), secondary synchronization signal (SSS), and cell-specificreference signal (CRS). A transmit (TX) multiple-input multiple-output(MIMO) processor 430 may perform spatial processing (e.g., precoding) onthe data symbols, the control symbols, and/or the reference symbols, ifapplicable, and may provide output symbol streams to the modulators(MODs) 432 a through 432 t. Each modulator 432 may process a respectiveoutput symbol stream (e.g., for OFDM, etc.) to obtain an output samplestream. Each modulator may further process (e.g., convert to analog,amplify, filter, and upconvert) the output sample stream to obtain adownlink signal. Downlink signals from modulators 432 a through 432 tmay be transmitted via the antennas 432 a through 432 t, respectively.

At the UE 120, the antennas 452 a through 452 r may receive the downlinksignals from the base station 110 and may provide received signals tothe demodulators (DEMODs) in transceivers 454 a through 454 r,respectively. Each demodulator 454 may condition (e.g., filter, amplify,downconvert, and digitize) a respective received signal to obtain inputsamples. Each demodulator may further process the input samples (e.g.,for OFDM, etc.) to obtain received symbols. A MIMO detector 456 mayobtain received symbols from all the demodulators 454 a through 454 r,perform MIMO detection on the received symbols if applicable, andprovide detected symbols. A receive processor 458 may process (e.g.,demodulate, deinterleave, and decode) the detected symbols, providedecoded data for the UE 120 to a data sink 460, and provide decodedcontrol information to a controller/processor 480.

On the uplink, at UE 120, a transmit processor 464 may receive andprocess data (e.g., for the physical uplink shared channel (PUSCH)) froma data source 462 and control information (e.g., for the physical uplinkcontrol channel (PUCCH) from the controller/processor 480. The transmitprocessor 464 may also generate reference symbols for a reference signal(e.g., for the sounding reference signal (SRS)). The symbols from thetransmit processor 464 may be precoded by a TX MIMO processor 466 ifapplicable, further processed by the demodulators in transceivers 454 athrough 454 r (e.g., for SC-FDM, etc.), and transmitted to the basestation 110. At the BS 110, the uplink signals from the UE 120 may bereceived by the antennas 434, processed by the modulators 432, detectedby a MIMO detector 436 if applicable, and further processed by a receiveprocessor 438 to obtain decoded data and control information sent by theUE 120. The receive processor 438 may provide the decoded data to a datasink 439 and the decoded control information to the controller/processor440.

The controllers/processors 440 and 480 may direct the operation at thebase station 110 and the UE 120, respectively. The processor 440 and/orother processors and modules at the BS 110 may perform or direct theexecution of processes for the techniques described herein. The memories442 and 482 may store data and program codes for BS 110 and UE 120,respectively. A scheduler 444 may schedule UEs for data transmission onthe downlink and/or uplink.

FIG. 5 illustrates a diagram 500 showing examples for implementing acommunications protocol stack, according to aspects of the presentdisclosure. The illustrated communications protocol stacks may beimplemented by devices operating in a wireless communication system,such as a 5G system (e.g., a system that supports uplink-basedmobility). Diagram 500 illustrates a communications protocol stackincluding a Radio Resource Control (RRC) layer 510, a Packet DataConvergence Protocol (PDCP) layer 515, a Radio Link Control (RLC) layer520, a Medium Access Control (MAC) layer 525, and a Physical (PHY) layer530. In various examples, the layers of a protocol stack may beimplemented as separate modules of software, portions of a processor orASIC, portions of non-collocated devices connected by a communicationslink, or various combinations thereof. Collocated and non-collocatedimplementations may be used, for example, in a protocol stack for anetwork access device (e.g., ANs, CUs, and/or DUs) or a UE.

A first option 505-a shows a split implementation of a protocol stack,in which implementation of the protocol stack is split between acentralized network access device (e.g., an ANC 202 in FIG. 2) anddistributed network access device (e.g., DU 208 in FIG. 2). In the firstoption 505-a, an RRC layer 510 and a PDCP layer 515 may be implementedby the central unit, and an RLC layer 520, a MAC layer 525, and a PHYlayer 530 may be implemented by the DU. In various examples the CU andthe DU may be collocated or non-collocated. The first option 505-a maybe useful in a macro cell, micro cell, or pico cell deployment.

A second option 505-a shows a unified implementation of a protocolstack, in which the protocol stack is implemented in a single networkaccess device. In the second option, RRC layer 510, PDCP layer 515, RLClayer 520, MAC layer 525, and PHY layer 530 may each be implemented bythe AN. The second option 505-a may be useful in, for example, a femtocell deployment.

Regardless of whether a network access device implements part or all ofa protocol stack, a UE may implement an entire protocol stack as shownin 505-c (e.g., the RRC layer 510, the PDCP layer 515, the RLC layer520, the MAC layer 525, and the PHY layer 530).

In LTE, the basic transmission time interval (TTI) or packet duration isthe 1 ms subframe. In NR, a subframe is still 1 ms, but the basic TTI isreferred to as a slot. A subframe contains a variable number of slots(e.g., 1, 2, 4, 8, 16, . . . slots) depending on the subcarrier spacing.The NR RB is 12 consecutive frequency subcarriers. NR may support a basesubcarrier spacing of 15 KHz and other subcarrier spacing may be definedwith respect to the base subcarrier spacing, for example, 30 kHz, 60kHz, 120 kHz, 240 kHz, etc. The symbol and slot lengths scale with thesubcarrier spacing. The CP length also depends on the subcarrierspacing.

FIG. 6 is a diagram showing an example of a frame format 600 for NR. Thetransmission timeline for each of the downlink and uplink may bepartitioned into units of radio frames. Each radio frame may have apredetermined duration (e.g., 10 ms) and may be partitioned into 10subframes, each of 1 ms, with indices of 0 through 9. Each subframe mayinclude a variable number of slots depending on the subcarrier spacing.Each slot may include a variable number of symbol periods (e.g., 7 or 14symbols) depending on the subcarrier spacing. The symbol periods in eachslot may be assigned indices. A mini-slot, which may be referred to as asub-slot structure, refers to a transmit time interval having a durationless than a slot (e.g., 2, 3, or 4 symbols).

Each symbol in a slot may indicate a link direction (e.g., DL, UL, orflexible) for data transmission and the link direction for each subframemay be dynamically switched. The link directions may be based on theslot format. Each slot may include DL/UL data as well as DL/UL controlinformation.

In NR, a synchronization signal (SS) block is transmitted. The SS blockincludes a PSS, a SSS, and a two symbol PBCH. The SS block can betransmitted in a fixed slot location, such as the symbols 0-3 as shownin FIG. 6. The PSS and SSS may be used by UEs for cell search andacquisition. The PSS may provide half-frame timing, the SS may providethe CP length and frame timing. The PSS and SSS may provide the cellidentity. The PBCH carries some basic system information, such asdownlink system bandwidth, timing information within radio frame, SSburst set periodicity, system frame number, etc. The SS blocks may beorganized into SS bursts to support beam sweeping. Further systeminformation such as, remaining minimum system information (RMSI), systeminformation blocks (SIBs), other system information (OSI) can betransmitted on a physical downlink shared channel (PDSCH) in certainsubframes.

In some circumstances, two or more subordinate entities (e.g., UEs) maycommunicate with each other using sidelink signals. Real-worldapplications of such sidelink communications may include public safety,proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V)communications, Internet of Everything (IoE) communications, IoTcommunications, mission-critical mesh, and/or various other suitableapplications. Generally, a sidelink signal may refer to a signalcommunicated from one subordinate entity (e.g., UE1) to anothersubordinate entity (e.g., UE2) without relaying that communicationthrough the scheduling entity (e.g., UE or BS), even though thescheduling entity may be utilized for scheduling and/or controlpurposes. In some examples, the sidelink signals may be communicatedusing a licensed spectrum (unlike wireless local area networks, whichtypically use an unlicensed spectrum).

A UE may operate in various radio resource configurations, including aconfiguration associated with transmitting pilots using a dedicated setof resources (e.g., a radio resource control (RRC) dedicated state,etc.) or a configuration associated with transmitting pilots using acommon set of resources (e.g., an RRC common state, etc.). Whenoperating in the RRC dedicated state, the UE may select a dedicated setof resources for transmitting a pilot signal to a network. Whenoperating in the RRC common state, the UE may select a common set ofresources for transmitting a pilot signal to the network. In eithercase, a pilot signal transmitted by the UE may be received by one ormore network access devices, such as an AN, or a DU, or portionsthereof. Each receiving network access device may be configured toreceive and measure pilot signals transmitted on the common set ofresources, and also receive and measure pilot signals transmitted ondedicated sets of resources allocated to the UEs for which the networkaccess device is a member of a monitoring set of network access devicesfor the UE. One or more of the receiving network access devices, or a CUto which receiving network access device(s) transmit the measurements ofthe pilot signals, may use the measurements to identify serving cellsfor the UEs, or to initiate a change of serving cell for one or more ofthe UEs.

Example Demodulation Reference Signal Design

Aspects of the present disclosure relate to conveying timing informationregarding a cell to a UE. For example, a BS may generate and transmitreference signals (e.g., a PSS, a SSS, and/or a DMRS) for each cellsupported by the BS.

In certain aspects, a BS (e.g., BS 110 described with respect to FIG. 1)is configured to transmit reference signals in blocks, which may bereferred to as synchronization signal blocks (SSBs). FIG. 7 illustratesan example of a SSB 700, in accordance with certain aspects. The X-axisin the illustration of FIG. 7 indicates time (e.g., symbols), and theY-axis indicates frequency (e.g., tones). As shown, SSB 700 includes aPSS 702, a SSS 704, a PBCH 706, and a PBCH 707 multiplexed in the timedomain and allocated to certain frequency ranges. In certain aspects,the PSS 702 and SSS 704 are allocated to the same frequency range.Further, in certain aspects, the PBCH 706 and PBCH 707 are allocated tothe same frequency range. In certain aspects, the PSS 702 and SSS 704are allocated to a portion (e.g., half) of the frequency range of thePBCH 706 and PBCH 707. Though shown in a particular order in SSB 700 andof particular durations and frequency allocations, it should be notedthat the order, durations, and frequency allocations of the PSS 702, SSS704, PBCH 706, and PBCH 707 may be different. Further, the SSB 700 mayinclude additional or fewer reference signals or additional or fewerPBCH. Further, in certain aspects, for each of PBCH 706 and PBCH 707,certain portions (e.g., frequency ranges, tones, resource elements(REs)) are allocated to transmission of reference sequences, such as inDMRS 710. It should be noted that though certain aspects are describedherein with respect to a DMRS in a SSB, other types of referencesequences may similarly be selected and included in the SSB instead. Incertain aspects, the allocation may be different than shown in FIG. 7.

Though not shown a SSB may include additional or fewer signals,channels, etc. than shown. For example, a SSB may further include athird synchronization signal (TSS) or a beam reference signal.

In certain aspects, multiple SSBs (e.g., SSB 700) may be assigned to aset of resources to transmit the multiple SSBs (such a set of resourcesfor transmitting multiple SSBs may be referred to herein as a SS burstset). The multiple SSBs may be assigned to periodic resources (e.g.,every 20 ms) and transmitted periodically by a BS (e.g., BS 110) in acell. For example, a SS burst set may include a number L of SSBs (e.g.,4, 8, or 64). In certain aspects the number L of SSBs included in a SSburst set is based on the frequency band used for transmission. Forexample, for sub 6 GHz frequency transmissions, L may equal 4 or 8. Inanother example, for transmission above 6 GHz, L may equal 64. Forexample, transmission by the BS 110 in a cell may be beamformed, so thateach transmission only covers a portion of the cell. Therefore,different SSBs in a SS burst set may be transmitted in differentdirections so as to cover the cell.

FIG. 8 illustrates an example of the timing of transmission of SSBs, inaccordance with certain aspects. As shown, a SS burst set 805 may betransmitted periodically every X msec (e.g., X=20). Further, the SSburst set 805 may have a duration of Y msec (e.g., Y<5), wherein all ofthe SSBs 810 in the SS burst set 805 are transmitted within the durationY. As shown in FIG. 8, each SSB 810 includes a PSS, SSS, and PBCH. SSB810 may for example, correspond to a SSB 700. SS burst set 805 includesa maximum of L SSBs 810 each having a corresponding SSB index (e.g., 0through L-1) indicating its location within the SS burst set, e.g.indicating the physical transmission ordering in time of the SSBs 810.Though the SSBs 810 are shown allocated in time consecutively in SSburst set 805, it should be noted that the SSBs 810 may not be allocatedconsecutively. For example, there may be separation in time (e.g., ofthe same or different durations) between the SSBs 810 in the SS burstset 805. The allocation of time of the SSBs 810 may correspond to aparticular pattern, which may be known to the BS 110 and UE 120.

In certain aspects, a SSB transmitted by a BS 110 to a UE 120 is used toconvey timing information about a cell served by the BS 110 to the UE120. For example, in certain aspects, the SSB is used to indicate thesystem frame number (SFN) level timing in the cell. In an example, theperiodic timing in the cell may be divided into system frames (e.g.,1024 system frames having a duration of 10 ms each). Therefore, eachsystem frame is assigned a sequential number (e.g., from 0-1023). Inthis example, the SSB is used to convey bits (e.g., 10 bitscorresponding to 2¹⁰ system frames) of information (e.g., in a payloadof the SSB, based on a configuration of the SSB, etc.) to indicate theSFN in which the SSB is transmitted, so the UE has timing information tothe SFN level (e.g., 10 ms level of timing).

In certain aspects, the SSB may additionally be used to conveyinformation about the timing within a system frame (e.g., sub-10 mstiming). For example, the SSB may be used to convey an additional bit(e.g., an 11^(th)bit) (e.g., in a payload of the SSB, based on aconfiguration of the SSB, etc.) to indicate a half system frame (e.g., 5ms) interval level of timing (e.g., indicating the first half/preambleof the system frame or the second half/mid-amble of the system frame inwhich the SSB is transmitted).

In certain aspects, the bits for SFN level timing and additional bit forhalf SFN level timing may be sufficient to indicate the timing oftransmission of a SS burst set (e.g., 5 ms). However, these bits may notbe sufficient to indicate the timing level within the SS burst set.Accordingly, in certain aspects, the timing level within the SS burstset may be indicated by the index of the individual SSBs transmitted inthe SS burst set. For example, as discussed, a UE 120 has informationregarding the pattern of the SSBs in the SS burst set. Accordingly, ifthe UE 120 has information regarding when a SSB having a particular SSBindex is transmitted within the SS burst set, and determines the SSBindex of a received SSB, it can determine the timing within the SS burstset synchronized to the received SSB. Therefore, in certain aspects theSSB may additionally be used to convey bits of information indicative ofthe SSB index of the SSB. For example, where there is a maximum of L=64SSBs, an additional 6 bits (e.g., 2⁶32 64) may be conveyed by the SSB toindicate the SSB index of the SSB. In certain aspects, therefore, theSSB may convey 17 bits (e.g., 10+1+6) bits of information.

In certain aspects, a number of bits (e.g., 3 bits) may be conveyedbased on a reference sequence, such as a DMRS sequence, used in a SSB.Though certain aspects are described with respect to a DMRS sequence,other types of sequences may be used. For example, there may be multiplecandidate DMRS sequences (e.g., 8) that may be used for the DMRS in aSSB, and the actual DMRS transmitted in the SSB may be indicative of thevalue (e.g., 000 through 111) of the number of bits.

For example, in certain aspects, the DMRS is a function of the cell IDof the cell in which the BS 110 transmits the SSB. In certain aspects,the UE 120 utilizes the PSS and/or SSS in the SSB to determine the cellID of the cell in which the SSB is transmitted. Further, for a givencell, there may be a number (e.g., 8) of candidate DMRS sequences thatmay be used. Therefore, the UE 120, based on the cell ID determined fromthe PSS and/or SSS may try correlating the received DMRS sequence in theSSB with each of the number of candidate DMRS sequences for the cell ID.The candidate DMRS sequence with the highest correlation to the receivedDMRS sequence in the SSB may be the DMRS sequence used in the SSB, andtherefore the UE 120 maps the DMRS sequence to a value of a number ofbits (e.g., 3).

In certain aspects, a number of bits (e.g., 14 bits) may be conveyed bythe PBCH of the SSB, e.g. explicitly in a payload of the PBCH and/orimplicitly (e.g., through PBCH scrambling (or redundancy version) wheredifferent scrambling sequences (redundancy versions) correspond todifferent values of a number of bits). For example, similar to the DMRSsequence, a UE 120 may try to descramble the PBCH using each of a numberof different candidate sequences (e.g., 4 candidate sequences to convey2 bits). The correct candidate sequence that decodes the PBCH in the SSBmay be the sequence used for scrambling the PBCH, and therefore the UE120 maps the sequence to a value of a number of bits (e.g., 2).

In certain aspects, the payload of the PBCH may be transmittedcorresponding to a transmission timing interval (TTI) (e.g. a broadcastchannel (BCH) TTI). For example, the payload of the PBCH may not changefor a BCH TTI duration (e.g., 80 ms). This may allow the UE to combinemultiple instances of received PBCH within the BCH TTI to improve thedecoding performance. Accordingly, in certain aspects, the payload ofthe PBCH in multiple consecutive SS burst sets (e.g., 4) is the same.Therefore, a UE 120 receiving the SS burst sets with the same PBCHpayload can combine the received PBCH payloads of the multiple SS burstsets to better decode the PBCH payload/improve detection (e.g., if thereis low SNR, interference, etc.). In another example, the UE 120 may beable to test different sequences for descrambling PBCH over different SSburst sets, such as if the UE 120 does not have memory/processingcapability to test all possible hypothesis sequences in a single SSburst set. However, in certain aspects, testing a number of differentsequences may introduce complexity and latency for performing the blinddecoding. Accordingly, certain aspects herein indicate to the UE 120 thePBCH scrambling sequence used in the SSB to allow the UE 120 to utilizethe proper scrambling sequence to descramble PBCH without testing eachpossible sequence.

In some aspects, there is no DMRS randomization across a SS burst set,meaning for a given cell ID, the DMRS sequence used in a SSB is basedsolely on the SSB index. For example, if DMRS sequences 1-6 are in orderfor the SSBs in a SS burst set, the same DMRS sequences 1-6 are used inorder for the SSBs in the following SS burst set. If there are twoneighboring cells that are synchronized (or not) that transmit theSSB/DMRS on overlapping resources there may be collisions at the UEreceiving the SSB/DMRS from each of the neighboring cells. If there isno DMRS randomization, then the same set of DMRS sequences are receivedfrom the neighboring cells (e.g., potentially a different DMRS sequencefrom each cell) for a given SSB index in each SS burst set. If the DMRSsequences of the set of DMRS sequences happen to have a high crosscorrelation, the UE 120 may not be able to properly detect the DMRS.Without DMRS randomization, this may lead to the UE 120 not being ableto properly detect the DMRS for each SS burst set. With DMRSrandomization, the chance that the DMRS sequences of the set have a highcross correlation in every SS burst set decreases, thereby potentiallymitigating detecting issues.

In certain aspects, the DMRS indicates a logical SSB index of the SSBinstead of the actual physical SSB index of the SSB. For example, asdiscussed, each SSB is physically located in time in a physical indexorder in the SS burst set. However, instead of the DMRS directlyindicating the physical index of the SSB, the DMRS may indicate alogical SSB index that is mapped (e.g., by a function, table, etc.) tothe physical SSB index of the SSB. For example, each physical SSB indexmay be mapped to a different value corresponding to a logical SSB index(e.g., 0, 1, 2, 3, 4, 5, 6, 7 are mapped to 2, 3, 4, 5, 6, 7, 0, 1,respectively). Therefore, in certain aspects, for a given SSB having agiven physical SSB index, the DMRS sequence transmitted in the physicalSSB index is based on the logical SSB index associated with the physicalSSB index.

In certain aspects, the mapping from the physical SSB index to thelogical SSB index is a function of some timing information of the cell.For example, the mapping may be a function of a SS burst set indexwithin a BCH TTI the SSB is transmitted. As discussed, a number ofconsecutive sets of resources corresponding to SS burst sets may be usedfor transmitting in a BCH TTI, and each may have a set index of theplurality of sets of resources referred to as a SS burst set indexcorresponding to its position in the BCH TTI. Additionally oralternatively, the mapping from the physical SSB index to the logicalSSB index is a function of a cell ID in which the SSB is transmitted.

By using the DMRS to indicate a logical SSB index instead of a physicalSSB index certain advantages may be realized. For example, by basing thelogical SSB index on the SS burst set index, there is DMRS randomizationacross different SS burst set indexes, thereby potentially mitigationdetecting issues as discussed. However, in such an example, to map thelogical SSB index to the physical SSB index, the UE 120 may needknowledge of the BCH TTI boundaries to know the SS burst set index. TheUE 120 may determine such information regarding BCH TTI boundaries for aserving cell of the UE by decoding PBCH (which includes informationabout the SS burst set index), which UE 120 may need to perform anywayduring initial cell acquisition. Further, for determining suchinformation for a neighboring cell the UE may receive timing informationof the neighboring cell from the serving cell explicitly as anindication, or may derive it based on the service cell timing where theserving cell and neighboring cell are synchronized within a maximumtiming offset (e.g., within +/− 10 ms).

In certain aspects, the DMRS indicates a logical SSB index of the SSBinstead of the actual physical SSB index of the SSB for only certaincells, frequency bands (e.g., above 6 GHz), numerologies (e.g., for 240KHz tone spacing), deployments (e.g., deployments with synchronouscells), scenarios (e.g., non-standalone operation, initial acquisitionsynchronization, synchronization for a one or more UEs in an RRC-idle orRRC-connected mode), etc. In other situations, the DMRS may indicate theactual physical SSB index.

In certain aspects, the mapping of physical SSB index in a SS burst setto a logical SSB index in a SS burst set may not be dependent on thecell ID or the SS burst set index. In certain aspects, the physical tological SSB index mapping may be according to the following equation(1):

l(p, c, b)=f(p)∀p,c,b   (1)

Here, p is the physical SSB index of the SSB in a SS burst set (e.g., p∈{0,1, . . . , L−1}(e. g., L=4, 8, 64)); c is the cell ID of the cellthe SSB is transmitted in (e.g., c∈{0,1, . . . , 1007}); b is the SSburst set index (e.g. within BCH TTI) of the SS burst set the SSB istransmitted in (e.g., b ∈{0,1,2,3}); l is the logical SSB index of theSSB in a SS burst set (e.g., l(p, c, b)∈{0,1, . . . L′−1) (e.g.,L′=4,8,64), L′ may be the same as or different from L); and f (p) is afunction of physical index p, for example f (p)=p or f(p)=mod (p, L′).While in general, the logical index l can be a function of anycombination of p, c, and b; in an example corresponding to equation 1, ldoes not depend on the cell ID c or SS burst set index b. In certainaspects, equation 1 provides no DMRS randomization. For example, theDMRS sequence indicates the physical SSB index such as shown accordingto the following table 1 based on equation 1 (where f (p)=p and p=(0:7)for each b maps to 1=(0,1,2,3,4,5,6,7)). In this table, l(0:7, c, b) isused to denote the sequence of logical SSB indices, for physical indicesp=(0,1,2, . . . , 7), for a given cell ID c and SS burst set index b:

TABLE 1 b 0 1 2 3 l(0:7, c, b) (0, 1, 2, 3, (0, 1, 2, 3, (0, 1, 2, 3,(0, 1, 2, 3, 4, 5, 6, 7) 4, 5, 6, 7) 4, 5, 6, 7) 4, 5, 6, 7)

In certain aspects, the mapping of physical SSB index in a SS burst setto a logical SSB index in a SS burst set may be dependent on the burstset index. In certain aspects, the physical to logical index mapping maybe according to the following equation (2):

l(p,c,b+1)=l(p,c,b)+Δ∀p,c,b   (2)

and for the burst set index b=0, the mapping may be

l(p,c,0)=mod (p, L′) ∀p,c

Here, Δ may be a constant non-zero value (for example Δ=1,2, . . . ,L′−1; more specifically Δ may be chosen such that a physical index mapsto the same logical index at the beginning of each BCH TTI (e.g. Δ=2when L′=8 and b=0,1,2,3)). The summation in equation 2 may be in moduloL′, to make sure 1 takes values in (0,1, . . . , L′−1)). In certainaspects, equation 2 provides some DMRS randomization as the mapping ofphysical SSB index in a SS burst set index to a logical SSB index isbased on the SS burst set index. For example, the mapping of physicalSSB index to logical SSB index is different for different values of bsuch as shown according to the following table 2 based on equation 2 andfor Δ=2:

TABLE 2 b 0 1 2 3 l(0:7, c, b) (0, 1, 2, 3, (2, 3, 4, 5, (4, 5, 6, 7,(6, 7, 0, 1, 4, 5, 6, 7) 6, 7, 0, 1) 0, 1, 2, 3) 2, 3, 4, 5)

In certain aspects, the design based on equation 2 exploits thedirectionality (e.g., beamforming) of SSB transmissions. For example, iftwo neighboring cells are each beamforming in different directions, thenthe UE 120 may receive SSB from one or both of the cells on only aparticular SSB within a SSB burst. In this example, for each SS burstset index, different pairs of DMRS sequences (corresponding to thedifferent logical SSB indexes) are transmitted for a given SSB index,thereby reducing the likelihood that the pair of DMRS sequences have ahigh correlation for the given SSB index in each SS burst set index.

In certain aspects, the design based on equation 2 allows a UE 120 tocombine DMRS for SSBs both within the same and across different SSBbursts to perform hypothesis checking (to determine the actual DMRSsequence as discussed). In particular, the logical indices correspondingto the DMRS sequences in consecutive SSBs in a SSB burst are incrementedby 1, so if the UE 120 can detect two consecutive or non-consecutiveSSBs it knows the incrementing in logical index used for DMRS sequencesand can combine the DMRS sequences. Similarly, DMRS sequences at thesame physical SSB index in consecutive SS burst sets (e.g. at leastwithin a BCH TTI) are incremented by A, so the UE 120 can combine theDMRS sequences.

In certain aspects, the mapping of physical SSB index in a SS burst setto a logical SSB index in a SS burst set may depend on both cell ID andburst set index. In certain aspects, the physical to logical indexmapping may be according to the following equation (3):

l(p,c,b+1)=l(p,c,b)+δ(c) ∀p,c,b   (3)

Where δ(c) is a value (e.g. in 0,1, . . . , L′) that depend on the cellid c. For example, we may haveδ(c)=mod(c, L′)

-   and for the burst set index b=0, the mapping may be

l(p,c,0)=mod (p, L′) ∉p,c

The summation in equation 3 may be in modulo L′, to make sure l takesvalues in (0,1 , . . . , L′−1)). In certain aspects, equation 3 providesadditional DMRS randomization as the mapping of physical SSB index in aSS burst set to a logical SSB index is based on the cell ID and the SSburst set index. For example, the mapping of physical SSB index tological SSB index is different for different values of b and c such asshown according to the following table 3 based on equation 3:

TABLE 3 b 0 1 2 3 mod(c, 8) 0 (0, 1, 2, 3, (0, 1, 2, 3, (0, 1, 2, 3, (0,1, 2, 3, 4, 5, 6, 7) 4, 5, 6, 7) 4, 5, 6, 7) 4, 5, 6, 7) 1 (0, 1, 2, 3,(1, 2, 3, 4, (2, 3, 4, 5, (3, 4, 5, 6, 4, 5, 6, 7) 5, 6, 7, 0) 6, 7,0, 1) 7, 0, 1, 2) 2 (0, 1, 2, 3, (2, 3, 4, 5, (4, 5, 6, 7, (6, 7, 0, 1,4, 5, 6, 7) 6, 7, 0, 1) 0, 1, 2, 3) 2, 3, 4, 5) 3 (0, 1, 2, 3, (3, 4, 5,6, (6, 7, 0, 1, (1, 2, 3, 4, 4, 5, 6, 7) 7, 0, 1, 2) 2, 3, 4, 5) 5, 6,7, 0) 4 (0, 1, 2, 3, (4, 5, 6, 7, (0, 1, 2, 3, (4, 5, 6, 7, 4, 5, 6, 7)0, 1, 2, 3) 4, 5, 6, 7) 0, 1, 2, 3) 5 (0, 1, 2, 3, (5, 6, 7, 0, (2, 3,4, 5, (7, 0, 1, 2, 4, 5, 6, 7) 1, 2, 3, 4) 6, 7, 0, 1) 3, 4, 5, 6) 6 (0,1, 2, 3, (6, 7, 0, 1, (4, 5, 6, 7, (2, 3, 4, 5, 4, 5, 6, 7) 2, 3, 4, 5)0, 1, 2, 3) 6, 7, 0, 1 7 (0, 1, 2, 3, (7, 0, 1, 2, (6, 7, 0, 1, (5, 6,7, 0, 4, 5, 6, 7) 3, 4, 5, 6) 2, 3, 4, 5) 1, 2, 3, 4)

In certain aspects, the design based on equation 3 is similar to thedesign based on equation 2, except that the amount that logical SSBindex of a SSB is incremented from one SSB burst index to the next isbased on c and is not just a constant value Δ as in equation 2.

In certain aspects, the mapping of physical SSB index in a SS burst setto a logical SSB index in a SS burst set may be according to thefollowing equation (4):

l(p,c,b+1)=l(p,c,b)+δ(c,b)∉p,c,b   (4)

and for the burst set index b=0, the mapping may be

l(p,c,0)=mod(p,L′)∉p,c

The summation in equation 4 may be in modulo L′, to make sure l takesvalues in (0,1, . . . , L′−1)). In certain aspects, equation 4 providesadditional DMRS randomization as the mapping of physical SSB index in aSS burst set to a logical SSB index is based on the cell ID and the SSburst set index similar to equation 3. However, instead of the amountthat logical SSB index of a SSB is incremented from one SSB burst indexto the next being based on c only as in equation 3, the amount thatlogical SSB index of a SSB is incremented from one SSB burst index tothe next is based on b and c. Accordingly, in certain aspects, when theUE 120 receives DMRS sequences in the same or different physical SSB inconsecutive or non-consecutive SS burst sets, it can look at thedifference between the DMRS sequences (e.g. the difference between thecorresponding logical indices) and based on the difference determine theSS burst set index of the SS burst sets because the delta differencebetween the DMRS sequences is specific to the SS burst sets.

In certain aspects, for a given c, the value of δ(c, b) for eachpossible value (or at least some of the values) of b is different (e.g.,δ(c, 0)≠ δ(c,1) ≠ δ(c,2)≠ δ(c,3)) to allow the UE 120 to determine theSS burst set index at least partly based on two DMRS received in twodifferent SS burst sets. In certain aspects, the summation of the valuesof δ(c, b) for each possible value of b modulo L′ is 0 in order to wraparound to the same initial state at the beginning of the next BCH TTI(e.g., mod(δ(c,0)+δ(c,1)+δ(c, 2)+δ(c,3), 8)=0). For example, the valueof δ(c, b) may be based on equation 5 as follows:

$\begin{matrix}{{\delta \left( {c,b} \right)} = \left\{ \begin{matrix}{{{mod}\left( {{{{mod}\left( {c,8} \right)} + {2b}},8} \right)}\mspace{115mu}} & {{{mod}\left( {c,2} \right)} = 1} \\{{mod}\left( {{{{mod}\left( {c,8} \right)} + \frac{b\left( {b + 3} \right)}{2}},8} \right)} & {{{{mod}\left( {c,2} \right)} = 0}\mspace{34mu}}\end{matrix} \right.} & (5)\end{matrix}$

For example, the mapping of physical SSB index to logical SSB index isdifferent for different values of b and c such as shown according to thefollowing table 4 based on equations 4 and 5:

TABLE 4 b 0 1 2 3 4 mod(c, 0 (0, 1, 2, 3, (0, 1, 2, 3, (2, 3, 4, 5, (7,0, 1, 2, (0, 1, 2, 3, 8) 4, 5, 6, 7) 4, 5, 6, 7) 6, 7, 0, 1) 3, 4, 5, 6)4, 5, 6, 7) 1 (0, 1, 2, 3, (1, 2, 3, 4, (4, 5, 6, 7, (1, 2, 3, 4, (0, 1,2, 3, 4, 5, 6, 7) 5, 6, 7, 0) 0, 1, 2, 3) 5, 6, 7, 0) 4, 5, 6, 7) 2 (0,1, 2, 3, (2, 3, 4, 5, (6, 7, 0, 1, (5, 6, 7, 0, (0, 1, 2, 3, 4, 5, 6, 7)6, 7, 0, 1) 2, 3, 4, 5) 1, 2, 3, 4) 4, 5, 6, 7) 3 (0, 1, 2, 3, (3, 4, 5,6, (0, 1, 2, 3, (7, 0, 1, 2, (0, 1, 2, 3, 4, 5, 6, 7) 7, 0, 1, 2) 4, 5,6, 7) 3, 4, 5, 6) 4, 5, 6, 7) 4 (0, 1, 2, 3, (4, 5, 6, 7, (2, 3, 4, 5,(3, 4, 5, 6, (0, 1, 2, 3, 4, 5, 6, 7) 0, 1, 2, 3) 6, 7, 0, 1) 7, 0, 1,2) 4, 5, 6, 7) 5 (0, 1, 2, 3, (5, 6, 7, 0, (4, 5, 6, 7, (5, 6, 7, 0, (0,1, 2, 3, 4, 5, 6, 7) 1, 2, 3, 4) 0, 1, 2, 3) 1, 2, 3, 4) 4, 5, 6, 7) 6(0, 1, 2, 3, (6, 7, 0, 1, (6, 7, 0, 1, (1, 2, 3, 4, (0, 1, 2, 3, 4, 5,6, 7) 2, 3, 4, 5) 2, 3, 4, 5) 5, 6, 7, 0) 4, 5, 6, 7) 7 (0, 1, 2, 3, (7,0, 1, 2, (0, 1, 2, 3, (3, 4, 5, 6, (0, 1, 2, 3, 4, 5, 6, 7) 3, 4, 5, 6)4, 5, 6, 7) 7, 0, 1, 2) 4, 5, 6, 7)

In certain aspects, as discussed, the number L of SSB in a SS burst setis based on the frequency range of transmission. Accordingly, in certainaspects, the number of possible DMRS sequences (e.g., 8) per cell ID maybe greater than the number of SSB (e.g., 4) in a SS burst set.Therefore, less than all of the defined DMRS sequences may be needed toindicate SSB index of the SSBs. Accordingly, in certain aspects,multiple DMRS sequences may be mapped to the same SSB index (e.g.,logical or physical SSB index). The DMRS sequence selected of themultiple DMRS sequences to indicate a given SSB index, therefore, may beused to convey additional information. In certain aspects the additionalinformation may be an extra bit. The extra bit may be used to indicatesystem information (e.g., extra timing information or non-timinginformation) about the cell. For example, the extra bit may indicate apart of the SFN and/or half-frame level timing (i.e., of the half-framethe SSB including DMRS is transmitted in). For example, the extra bitmay indicate the part of the 10-bit SFN that indicates the halfwayboundaries (e.g., 40 ms boundaries) in a BCH TTI. Accordingly, within aBCH TTI, the value of the bit for the consecutive SS burst sets withconsecutive SS burst set indexes will be 0,0,1,1. Therefore, thesequence of the value of the bit for two consecutive SS burst sets willbe 00, 01, 11, or 10, which are all different, and therefore can be usedto determine the SS burst set index for the SS burst sets. In anotherexample, the extra bit may indicate system configuration, operation mode(e.g., sync for initial acquisition, or for one or more UEs inidle/connected mode), sync burst set periodicity, SS burst setstructure, information to indicate whether UE can camp on this cell, anyinformation that can help UE in processing the PBCH channel, etc.

In another example, less than all of the defined DMRS sequences aretransmitted to indicate SSB index, and therefore the UE 120 may need toperform hypothesis testing for only a subset of DMRS sequences. Incertain aspects, the subset of DMRS sequences used may be dependent oncell ID or burst set index. The UE 120 may then need to performhypothesis testing for all of the DMRS sequences, but can also thenutilize the described logical to physical SSB index mapping techniques.

FIG. 9 illustrates example operations 900 for wireless communications,for example, for generating and communicating reference signals.According to certain aspects, operations 900 may be performed by a BS(e.g., one or more of the BSs 110).

Operations 900 begin at 902 where the BS selects a reference sequence ofa plurality of reference sequences to transmit in a cell in asynchronization signal block (SSB) based at least on a logical value,wherein the logical value is determined based on a SSB index indicatinga location of the SSB within a set of resources of a plurality of setsof resources and at least one of a cell ID of the cell, a set indexindicating a location of the set of resources within the plurality ofsets of resources, or a second value based on system informationcorresponding to the cell. At 904, the BS transmits the selectedreference sequence in the SSB.

FIG. 10 illustrates example operations 1000 for wireless communications,for example, for receiving reference signals and determining timinginformation based on the reference signals. According to certainaspects, operations 1000 may be performed by a user equipment (e.g., oneor more of the UEs 120).

Operations 1000 begin at 1002 where the UE receives a reference sequenceof a plurality of reference sequences. At 1004, the UE receives anindication of a cell ID associated with the reference sequence. At 1006,the UE determines timing information for the cell based on the referencesequence received and the cell ID. In certain aspects, the UE does notreceive the cell ID. In certain aspects, the UE determines half-frametiming information for the cell based on the reference sequence received(e.g., in a SSB).

FIG. 11 illustrates a communications device 1100 that may includevarious components (e.g., corresponding to means-plus-functioncomponents) configured to perform operations for the techniquesdisclosed herein, such as the operations illustrated in FIG. 9. Thecommunications device 1100 includes a processing system 1102 coupled toa transceiver 1108. The transceiver 1108 is configured to transmit andreceive signals for the communications device 1100 via an antenna 1110,such as the various signal described herein. The processing system 1102may be configured to perform processing functions for the communicationsdevice 1100, including processing signals received and/or to betransmitted by the communications device 1100.

The processing system 1102 includes a processor 1104 coupled to acomputer-readable medium/memory 1112 via a bus 1106. In certain aspects,the computer-readable medium/memory 1112 is configured to storeinstructions that when executed by processor 1104, cause the processor1104 to perform the operations illustrated in FIG. 9, or otheroperations for performing the various techniques discussed herein.

In certain aspects, the processing system 1102 further includes aselecting component 1114 for performing the operations illustrated in902 of FIG. 9. Additionally, the processing system 1102 includes atransmitting component 1116 for performing the operations illustrated in904 of FIG. 9. The selecting component 1114 and transmitting component1116 may be coupled to the processor 1104 via bus 1106. In certainaspects, the selecting component 1114 and transmitting component 1116may be hardware circuits. In certain aspects, selecting component 1114and transmitting component 1116 may be software components that areexecuted and run on processor 1104.

FIG. 12 illustrates a communications device 1200 that may includevarious components (e.g., corresponding to means-plus-functioncomponents) configured to perform operations for the techniquesdisclosed herein, such as the operations illustrated in FIG. 10. Thecommunications device 1200 includes a processing system 1202 coupled toa transceiver 1208. The transceiver 1208 is configured to transmit andreceive signals for the communications device 1200 via an antenna 1210,such as the various signal described herein. The processing system 1202may be configured to perform processing functions for the communicationsdevice 1200, including processing signals received and/or to betransmitted by the communications device 1200.

The processing system 1202 includes a processor 1204 coupled to acomputer-readable medium/memory 1212 via a bus 1206. In certain aspects,the computer-readable medium/memory 1212 is configured to storeinstructions that when executed by processor 1204, cause the processor1204 to perform the operations illustrated in FIG. 10, or otheroperations for performing the various techniques discussed herein.

In certain aspects, the processing system 1202 further includes areceiving component 1214 for performing the operations illustrated in1002 and 1004 of FIG. 10. Additionally, the processing system 1202includes a determining component 1216 for performing the operationsillustrated in 1006 of FIG. 10. The receiving component 1214 anddetermining component 1216 may be coupled to the processor 1204 via bus1206. In certain aspects, the receiving component 1214 and determiningcomponent 1216 may be hardware circuits. In certain aspects, receivingcomponent 1214 and determining component 1216 may be software componentsthat are executed and run on processor 1204.

FIG. 13 illustrates example operations 1300 for wireless communications,for example, for generating and communicating reference signals.According to certain aspects, operations 1300 may be performed by a BS(e.g., one or more of the BSs 110).

Operations 1300 begin at 1302 where the BS selects a demodulationreference sequence (DMRS) of a plurality of DMRSs for transmission in asynchronization signal block (SSB) based on a half-frame in which theSSB is transmitted. At 1304, the BS transmits the selected DMRS in theSSB.

FIG. 14 illustrates a communications device 1400 that may includevarious components (e.g., corresponding to means-plus-functioncomponents) configured to perform operations for the techniquesdisclosed herein, such as the operations illustrated in FIG. 13. Thecommunications device 1400 includes a processing system 1402 coupled toa transceiver 1408. The transceiver 1408 is configured to transmit andreceive signals for the communications device 1400 via an antenna 1410,such as the various signal described herein. The processing system 1402may be configured to perform processing functions for the communicationsdevice 1400, including processing signals received and/or to betransmitted by the communications device 1400.

The processing system 1402 includes a processor 1404 coupled to acomputer-readable medium/memory 1412 via a bus 1406. In certain aspects,the computer-readable medium/memory 1412 is configured to storeinstructions that when executed by processor 1404, cause the processor1404 to perform the operations illustrated in FIG. 13, or otheroperations for performing the various techniques discussed herein.

In certain aspects, the processing system 1402 further includes aselecting component 1414 for performing the operations illustrated in1302 of FIG. 13. Additionally, the processing system 1402 includes atransmitting component 1416 for performing the operations illustrated in1304 of FIG. 13. The selecting component 1414 and transmitting component1416 may be coupled to the processor 1404 via bus 1406. In certainaspects, the selecting component 1414 and transmitting component 1416may be hardware circuits. In certain aspects, selecting component 1414and transmitting component 1416 may be software components that areexecuted and run on processor 1404.

The methods disclosed herein comprise one or more steps or actions forachieving the methods. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover a, b, c,a-b, a-c, b-c, and a-b-c, as well as any combination with multiples ofthe same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b,b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language of the claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed under the provisions of 35U.S.C. §112(f) unless the element is expressly recited using the phrase“means for” or, in the case of a method claim, the element is recitedusing the phrase “step for.”

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

If implemented in hardware, an example hardware configuration maycomprise a processing system in a wireless node. The processing systemmay be implemented with a bus architecture. The bus may include anynumber of interconnecting buses and bridges depending on the specificapplication of the processing system and the overall design constraints.The bus may link together various circuits including a processor,machine-readable media, and a bus interface. The bus interface may beused to connect a network adapter, among other things, to the processingsystem via the bus. The network adapter may be used to implement thesignal processing functions of the PHY layer. In the case of a userterminal 120 (see FIG. 1), a user interface (e.g., keypad, display,mouse, joystick, etc.) may also be connected to the bus. The bus mayalso link various other circuits such as timing sources, peripherals,voltage regulators, power management circuits, and the like, which arewell known in the art, and therefore, will not be described any further.The processor may be implemented with one or more general-purpose and/orspecial-purpose processors. Examples include microprocessors,microcontrollers, DSP processors, and other circuitry that can executesoftware. Those skilled in the art will recognize how best to implementthe described functionality for the processing system depending on theparticular application and the overall design constraints imposed on theoverall system.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer readable medium.Software shall be construed broadly to mean instructions, data, or anycombination thereof, whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. The processor may beresponsible for managing the bus and general processing, including theexecution of software modules stored on the machine-readable storagemedia. A computer-readable storage medium may be coupled to a processorsuch that the processor can read information from, and write informationto, the storage medium. In the alternative, the storage medium may beintegral to the processor. By way of example, the machine-readable mediamay include a transmission line, a carrier wave modulated by data,and/or a computer readable storage medium with instructions storedthereon separate from the wireless node, all of which may be accessed bythe processor through the bus interface. Alternatively, or in addition,the machine-readable media, or any portion thereof, may be integratedinto the processor, such as the case may be with cache and/or generalregister files. Examples of machine-readable storage media may include,by way of example, RAM (Random Access Memory), flash memory, ROM (ReadOnly Memory), PROM (Programmable Read-Only Memory), EPROM (ErasableProgrammable Read-Only Memory), EEPROM (Electrically ErasableProgrammable Read-Only Memory), registers, magnetic disks, opticaldisks, hard drives, or any other suitable storage medium, or anycombination thereof. The machine-readable media may be embodied in acomputer-program product.

A software module may comprise a single instruction, or manyinstructions, and may be distributed over several different codesegments, among different programs, and across multiple storage media.The computer-readable media may comprise a number of software modules.The software modules include instructions that, when executed by anapparatus such as a processor, cause the processing system to performvarious functions. The software modules may include a transmissionmodule and a receiving module. Each software module may reside in asingle storage device or be distributed across multiple storage devices.By way of example, a software module may be loaded into RAM from a harddrive when a triggering event occurs. During execution of the softwaremodule, the processor may load some of the instructions into cache toincrease access speed. One or more cache lines may then be loaded into ageneral register file for execution by the processor. When referring tothe functionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

Also, any connection is properly termed a computer-readable medium. Forexample, if the software is transmitted from a website, server, or otherremote source using a coaxial cable, fiber optic cable, twisted pair,digital subscriber line (DSL), or wireless technologies such as infrared(IR), radio, and microwave, then the coaxial cable, fiber optic cable,twisted pair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein. For example, instructions for performing the operationsdescribed herein and illustrated in FIGS. 9, 10, and 13.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

What is claimed is:
 1. A method for communicating reference signals, themethod comprising: selecting a demodulation reference sequence (DMRS) ofa plurality of DMRSs for transmission in a synchronization signal block(SSB) based on a half-frame in which the SSB is transmitted; andtransmitting the selected DMRS in the SSB.
 2. The method of claim 1,wherein the half-frame is part of a system frame.
 3. The method of claim1, wherein the SSB is one of a plurality of SSBs in a synchronizationsignal (SS) burst set comprising four SSBs.
 4. The method of claim 3,wherein selecting the DMRS is further based on an index of the SSB. 5.The method of claim 4, wherein each of the plurality of SSBs istransmitted on a separate spatial beam.
 6. The method of claim 1,wherein the SSB includes a physical broadcast channel (PBCH).
 7. Themethod of claim 1, wherein selecting the DMRS is further based on anindex of the SSB.
 8. A wireless device comprising: a memory; and aprocess configured to: select a demodulation reference sequence (DMRS)of a plurality of DMRSs for transmission in a synchronization signalblock (SSB) based on a half-frame in which the SSB is transmitted; andtransmit the selected DMRS in the SSB.
 9. The wireless device of claim8, wherein the half-frame is part of a system frame.
 10. The wirelessdevice of claim 8, wherein the SSB is one of a plurality of SSBs in asynchronization signal (SS) burst set comprising four SSBs.
 11. Thewireless device of claim 10, wherein selecting the DMRS is further basedon an index of the SSB.
 12. The wireless device of claim 11, whereineach of the plurality of SSBs is transmitted on a separate spatial beam.13. The wireless device of claim 8, wherein the SSB includes a physicalbroadcast channel (PBCH).
 14. The wireless device of claim 8, whereinselecting the DMRS is further based on an index of the SSB.
 15. Awireless device comprising: means for selecting a demodulation referencesequence (DMRS) of a plurality of DMRSs for transmission in asynchronization signal block (SSB) based on a half-frame in which theSSB is transmitted; and means for transmitting the selected DMRS in theSSB.
 16. The wireless device of claim 15, wherein the half-frame is partof a system frame.
 17. The wireless device of claim 15, wherein the SSBis one of a plurality of SSBs in a synchronization signal (SS) burst setcomprising four SSBs.
 18. The wireless device of claim 17, whereinselecting the DMRS is further based on an index of the SSB.
 19. Thewireless device of claim 18, wherein each of the plurality of SSBs istransmitted on a separate spatial beam.
 20. The wireless device of claim15, wherein the SSB includes a physical broadcast channel (PBCH). 21.The wireless device of claim 15, wherein selecting the DMRS is furtherbased on an index of the SSB.
 22. A non-transitory computer readablestorage medium that stores instructions that when executed by a wirelessdevice cause the wireless device to perform a method for communicatingreference signals, the method comprising: selecting a demodulationreference sequence (DMRS) of a plurality of DMRSs for transmission in asynchronization signal block (SSB) based on a half-frame in which theSSB is transmitted; and transmitting the selected DMRS in the SSB. 23.The non-transitory computer readable storage medium of claim 22, whereinthe half-frame is part of a system frame.
 24. The non-transitorycomputer readable storage medium of claim 22, wherein the SSB is one ofa plurality of SSBs in a synchronization signal (SS) burst setcomprising four SSBs.
 25. The non-transitory computer readable storagemedium of claim 24, wherein selecting the DMRS is further based on anindex of the SSB.
 26. The non-transitory computer readable storagemedium of claim 25, wherein each of the plurality of SSBs is transmittedon a separate spatial beam.
 27. The non-transitory computer readablestorage medium of claim 22, wherein the SSB includes a physicalbroadcast channel (PBCH).
 28. The non-transitory computer readablestorage medium of claim 22, wherein selecting the DMRS is further basedon an index of the SSB.